1. Field of the Invention
The present invention relates to semiconductor substrate processing systems. More particularly, the present invention relates to techniques and apparatus for automatically determining whether a substrate process chamber matches a reference substrate process chamber and the potential source(s) of chamber fault.
2. Description of the Related Art
Within the semiconductor industry, an ever present need exists for improved process repeatability and control. As new generations of integrated circuits employ smaller feature sizes than were contemplated in previous generations, greater demands are placed on the integrated circuit fabrication process. Deposition and etching one or more layers of a semiconductor substrate in a plasma environment are two of the most common steps in integrated circuit manufacturing. To ensure that a correct quantity and quality of film is deposited or etched, the plasma state of the process chamber needs to be monitored comprehensively prior to, during and after production substrate processing. Comprehensive chamber monitoring prior to production substrate processing allows proper chamber qualification to be conducted. Comprehensive chamber monitoring during production substrate processing allows correct endpoint and fault detection. Comprehensive chamber monitoring after production substrate processing allows diagnosis of source of fault, if faults were detected during substrate processing.
To ensure that a correct amount and quality of film is deposited or etched, a process chamber needs to be monitored and be compared to a “reference” chamber (“good” chamber or “golden” chamber). The procedure used to compare chambers is sometimes called chamber qualification. Chamber qualification procedures are used at various times during a chamber's use. When a process chamber is newly manufactured, the chamber must be qualified. The new chamber needs to be matched to a “golden” chamber to ensure the new chamber will perform according to its specification. Once the chamber is qualified, the chamber can then be shipped to a semiconductor manufacturing facility. Once the chamber arrives at the semiconductor manufacturing facility, the chamber is reassembled and “qualified” again prior to processing the production materials. In addition, in a semiconductor manufacturing facility, a plasma deposition or etching chamber can potentially be used to run different process recipes for different substrates. Before a process recipe is changed, the chamber usually needs to be “qualified” again to ensure the chamber is operating normally before the process recipe change occurs. Lastly, production chambers must undergo regular maintenance or cleaning. After maintenance or chamber cleaning, the chamber needs to be “qualified” again prior to running production wafers. For new generation semiconductor manufacturing, stringent chamber matching techniques that utilize comprehensive plasma monitoring are needed to ensure process repeatability and control.
To ensure that a correct amount and quality of film is deposited or etched, substrate processing in a process chamber needs to be monitored during the processing. Plasma state of the process and chamber during processing needs to match that of a selected process in a “reference” chamber to ensure the chamber and process are functioning as expected and also correct endpoint detection can occur to terminate the process at the desired time. If the plasma state of the process and chamber during processing does not match that of a selected process in a “reference” chamber, a potential fault is detected and the operator is alarmed to take appropriate action. Details of how a chamber and process can be monitored during process to detect endpoint and fault have been disclosed in commonly assigned U.S. Pat. No. 6,368,975, entitled “Method and Apparatus For Monitoring A Process By Employing Principal component Analysis”, issued on Apr. 9, 2002 and its divisional application Ser. No. 10/341,696, filed on Jan. 14, 2003.
Besides chamber qualification, process monitoring and endpoint detection, techniques for identifying the source of a chamber fault are also very much in demand. In a semiconductor manufacturing environment, chambers can be found to have insufficient pre-conditioning, such as seasoning, or to have hardware related problems. It's important to quickly determine the sources of the problem (or fault) to reduce the down time of the processing equipment. Extended down time can be very costly.
During a plasma process, certain plasma “attributes”, such as the plasma's electromagnetic emissions, the RF power delivered to a wafer pedestal, wafer reflectance, process pressure and process temperature, manifest low frequency fluctuations that contain significant information about the plasma process and the plasma chamber. The intensity of a plasma's optical electromagnetic emission (OES) and the fluctuations of the RF power delivered to a wafer pedestal during plasma processing contain information related to process state, process event and process chamber. OES and RF states are affected to different degrees by varying chamber conditions and by process parameter changes. OES and RF data are complementary to one another. Inclusion of both data during process or chamber monitoring is more comprehensive than merely including one of the two types of data.
Therefore, there is a need in the art for techniques for automatically determining whether a substrate process chamber matches a reference substrate process chamber and the potential source(s) of chamber fault that are repeatable and accurate by comprehensive monitoring of semiconductor plasma processes.